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Viewing 1 to 30 of 74
2015-09-27
Technical Paper
2015-01-2685
Diego Masotti, Patric Neis, Ney Ferreira, Kássio Gomes, Jean Poletto, Luciano Matozo
The present work presents evaluation of the sliding surface morphology of brake pads during stick-slip process. For doing that, a brake friction material was subjected to slide against a brake disc under conditions favorable to produce stick-slip phenomenon. The experiments were conducted in a laboratory-scale tribometer, which was especially designed to test brake pads used in vehicle. Optical microscope images of the material’s surface were obtained at different stages of the braking test. These images were post-processed in appropriate computational software and by means of the segmentation technique the real contact area, size and amount of contact plateaus related to the brake pad surface were estimated. Coefficient of friction resulting from the tests was measured and it is also discussed throughout this paper.
2015-09-27
Technical Paper
2015-01-2684
Seongjoo Lee, ShinWook Kim, ShinWan Kim, Seong Rhee
A correlation between brake squeal and disc wear was reported previously. This investigation was undertaken to confirm the correlation and to characterize the disc wear particles transferred to the sliding surface of the NAO pad. It is found that the iron distribution on the pad is very non-uniform; at some locations, the iron concentration reaches the level of Low Steel Lomets (15-20wt%); and squealing brakes exhibit increased amounts of transferred disc wear particles on the pad surface. These transferred particles are found as small and flattened thin metallic sheets, which are different from relatively large “metal pick-up” pieces.
2015-09-27
Technical Paper
2015-01-2673
Toshikazu Okamura
Brake judder is one of the most serious problems in automotive-brake systems and brake discs play a significant role in judder. There are two types of brake judder: cold and hot. Hot judder is caused by the thermo-mechanical deformation of a disc rotor due to high-speed brakings. There are several causes and shapes of disc’s thermo-mechanical deformation, e.g. coning and wave-like shapes. The circumferential wave-like shapes of brake discs are typically found as a butterfly shape in the second order of the rotational speed and corrugation (or heat spots) around tenth order of that. They are caused by thermo-mechanical buckling and are the significant cause of hot judder. The author focuses on the effects of material and dimensional homogeneity on the transient and permanent deformation of ventilated discs in the low orders of the rotational speed during repetitive high-speed brakings.
2015-05-13
Technical Paper
2015-36-0019
Márcio J. Ciolfi, Paulo E. B. de Mello
Abstract This paper presents the different “gradients” of heat transfer coefficients found in a usual ventilated brake disc type. Although the conduction coefficient depends on the material characteristics applied, the convection and radiation coefficients changes as function of vehicle speed and brake temperature respectively. By comparing the coefficients magnitude orders of each surface and condition is possible to define the most favorable geometries for cool down the system.
2015-04-14
Journal Article
2015-01-0691
Salah H. R. Ali, Sarwat Z. A. Zahwi, Hassan H. Dadoura
Abstract The main aim of this work is to develop an identification method to demonstrate the crucial surfaces of automotive braking system. Two brand new brake discs manufactured by two different manufacturers are tested. A typical disc to the one of them was put under working condition in actual braking system. Dimensional and geometrical deviations are investigated using advanced engineering metrological technique. Mechanical properties, tribological characteristics and chemical analyses are investigated. A coordinate measuring machine, universal hardness tester, mass comparator and XRF spectrometer are used in these diagnoses. Measurements of dimensional and geometrical deviations such as disc thickness variations, thickness deviations, straightness, parallelism, runout of disc surfaces are conducted. A comparison between form deviations in disc surfaces have been carried out and analyzed.
2014-11-11
Journal Article
2014-32-0053
Yoshihiro Nakagawa, Shinya Takahashi, Mikihito Masaki, Ranju Imao
Abstract In brake squeal analyses using FE models, minimizing the discrepancies in vibration characteristics between the measurement and the simulation is a key issue for improving its reproducibility. The discrepancies are generally adjusted by the shape parameters and/or material properties applied to the model. However, the discrepancy cannot be easily adjusted, especially, for the vibration characteristic of the disc model of a motorcycle. One of the factors that give a large impact on this discrepancy is a thermal history of the disc. That thermal history includes the one experienced in manufacturing process. In this paper, we examine the effects of residual stress on the natural frequency of motorcycle discs. The residual stress on the disc surface was measured by X-ray stress measurement method. It was followed by an eigenvalue analysis. In this analysis, we developed a unique method in which the residual stress was substituted by thermal stress.
2014-09-28
Technical Paper
2014-01-2534
Liangxu Ma, Liangyao Yu, Xuhui Liu, Zhizhong Wang, Ning Pan
Abstract The paper is focused on the research of the automotive magneto-rheological brake system whose braking force comes from the shear stress of magneto-rheological fluid under the condition of magnetic field. The MRF brake is designed for an electric passenger car to replace a conventional hydraulic disc-type brake. The braking torque of this system can be linearly adjusted by the current in just a few milliseconds with proper materials. Therefore this system has a quick response and precise control performance with a low hysteresis. Nowadays, most of the related research of MRF is about the construction of the prototype and the realization of the brake force. Main limitation of MRF brake lies in the braking torque cannot meet the actual needs and the power consumption may be too much if it is not well designed. The prototype introduced in the SAE Brake Colloquium-31nd Annual has been manufactured and assembled critically.
2014-09-28
Technical Paper
2014-01-2519
ByeongUk Jeong, Hoon Kim, Woochul Kim, Sang Do Kwak
Abstract Owing to the enhanced performance of engines these days, more heat should be dissipated in the braking system. Failure of doing this properly causes temperature rise in the brake disc which result in the brake fade, disc distortion, brake judder, etc. A cooling-air-duct was proposed as a solution to prevent these from happening. In this paper, we present our work based on experiments optimized parameters such as direction, location, shapes and the size of the duct for the cooling-air-duct installation in real cars. We installed the duct extended from a front bumper to a rear wheel guard. Experimental parameters were compared with theoretical analysis using the impinging jet analysis. The heat transfer coefficients were determined by using the finite elements method (FEM). We found that our experimental data is supportive of theoretical analysis. We believe that our results should serve an useful guideline for designing the cooling-air-duct for braking system.
2014-09-28
Technical Paper
2014-01-2510
Jung Hoon Woo, Jeongkyu Kim, Kwang Yun Kim, Daekyung Ko
Abstract Creep groan noise occurs in a just moving vehicle by the simultaneous application of torque to the wheel and the gradual release of brake pressure in-vehicle. It is the low frequency noise giving the driver a very uncomfortable feeling. It is caused by the stick-sleep phenomenon at the lining and disc interface. Recently, the field claim of low frequency creep groan has increased. There are a lot of efforts to improve creep groan noise by means of modification of lining material. In this paper, Transfer path of creep groan noise was analyzed through ODS and TPA. Additionally the correlation between Source (Brake torque variation, Brake vibration) and Creep Groan Sound level was discussed. Finally countermeasure to Creep Groan noise was suggested.
2014-09-28
Technical Paper
2014-01-2513
Taeho Jung, Jeongkyu Kim
Abstract Rust accumulated on disc surfaces causes brake judder and grind noise. This paper deals with grind noise(wire brush brake noise) in vehicles which is a low frequency vibration and broadband noise problem at 100∼1kHz that appears in low vehicle speed. Recently, the customer complaints have increased for grind and creep groan noise more than squeal noise. Low frequency brake noise is a combined effect of brake and suspension systems working with each other. The noise transfer path is also important. Experimental results are confirmed through ODS, Modal, TPA and 3D acoustic camera for noise transmission path. Finally, reduction methods of grind noise are presented.
2014-09-28
Technical Paper
2014-01-2503
Johannes Schneider
The brake discs and brake drums used on motor vehicles are, in 90% of applications, made from grey cast iron. Although other designs such as composite systems comprising of a grey iron braking band and a light weight mounting bell made from aluminum, Al-MMC or entire ceramic brake discs have been developed, cast iron will continue to play a major role as a work piece material for brakes. Cast iron offers advantages in material characteristics such as good thermal conductivity, high compressive strength and damping capacity. In addition it shows a superior casting behavior and also an unbeatable competitive price per part, when compared to other brake materials or designs. Ongoing research in material and casting science are leading to new types of alloyed CI materials, fulfilling the increasing demands in terms of performance but also increasing the demands for a reliable and economical production.
2014-09-28
Technical Paper
2014-01-2505
Ashesh Shah, Sanjay Patil, Umesh Abhyankar
Abstract The customer satisfaction index is higher for disc brake systems because of the advantages like less reaction time, shorter stopping distance and improved pedal feel compared to drum brake system. In current competitive market scenario and as per customer requirements, front disc brake module is becoming necessary. The brake system design is challenging task due to stringent performance meeting criteria and packaging constraints with weight optimization. Brake disc is very important component in the brake system which is expected to withstand high braking torque and dissipate heat during braking event. In existing car to replace front drum brake with disc brake module, vehicle needs to undergo legislative verifications and certifications with respect to pedal effort, stopping distance and circuit failed conditions etc.
2014-09-28
Technical Paper
2014-01-2493
Juan Carlos Martinez Laurent, Adrian Jordan, Francisco Canales
Abstract The brake system and components are essential active safety systems for users of motor vehicles, one common NVH phenomenon known as Brake Disc Thermal Coning creates a perception of poor braking system performance. Although Brake Disc Thermal Coning does not deteriorate the braking distance or the vehicle performance, is a concern for the customer who identifies any undesired vibration as a potential performance loss resulting in complaints and warranty claims. In order to increase the quality, and reliability of the products, Automotive OEMs have created processes and tests, today incorporating the ones based in computational solutions, to identify, prevent and correct potential issues before its present in the final product.
2014-09-28
Technical Paper
2014-01-2482
Meechai Sriwiboon, Nipon Tiempan, Kritsana Kaewlob, Seong Kwan Rhee
The influence of processing conditions on Low-Copper NAO disc pads were investigated as part of an effort to develop Low-Copper disc pad formulations as this kind of information is not readily available in open literature. Processing conditions as well as formulation modifications are found to influence friction, pad wear, disc wear and brake squeal. Low-Copper disc pads for pick-up trucks, equivalent to an OE pad, are developed. It is also found that brake squeal measured during the SAE J2522 (AK Master) Performance testing is related to the combined total wear rate of the disc plus the inner/outer pads or the disc wear rate alone, and that there is a threshold wear rate, above which brake squeal increases rapidly.
2014-09-28
Journal Article
2014-01-2525
Tomasz Grabiec
Abstract Wear and friction behavior of disc brakes are important properties of disc brake systems and are mainly addressed by appropriate selection and tuning of friction material. Disc material composition is often considered as “given”. The most common material used for brake discs is grey cast iron which can have carbon content between 2.5 to 4.2 percent. It is difficult to find in literature investigations related to the influence of cast iron material in combination with modern low-met friction material on wear and friction performance of disc brakes. In this work, the author will try to analyze impact of brake disc material properties on wear and friction performance.
2014-09-28
Journal Article
2014-01-2502
Toshikazu Okamura
Abstract There are various processes for finishing the friction surfaces of a brake disc, which affect the braking effectiveness of a vehicle in the early stages of use in some cases. To examine the interaction between the disc surface texture, rotational direction, and friction material, a series of experiments on a tribotester using small-scale specimens was conducted. In a previous paper (2013-01-2056), the results from the first series of experiments, which involved of thirty disc surface textures and a less aggressive non-asbestos organic (NAO) friction material in on-brake-drag conditions combining constant speed and normal-load, was reported. Disc surfaces were finished by the following finishing processes in two rotational directions: turning under four cutting conditions, roller burnishing after turning, turning with a wiper insert, and grinding with two stones. Contact-pressure dependency of friction and wear was confirmed.
2014-09-28
Technical Paper
2014-01-2491
SeongJoo Lee, JooSeong Jeong, ShinWook Kim, ShinWan Kim, Seong Rhee
A previous investigation showed that minor variations in alloying elements in gray cast iron disc contributed to measurable differences in friction and disc wear. This investigation was undertaken to find out if and how the increased friction and disc wear might affect brake squeal. The SAE J2522 and J2521 dynamometer procedures as well as an OEM noise dynamometer procedure and a chassis dynamometer noise procedure were used to find out if a correlation between disc wear and brake squeal could be discovered. In all cases, as the wear rate of a disc increases under a given set of test conditions, disc material transfer to the pad surface increases, which results in increased friction and brake squeal. Also a good method to detect disc variability (disc to disc, within a disc) is discussed.
2014-09-28
Technical Paper
2014-01-2486
Axel Stenkamp, Michael Schorn
Abstract Starting in the late '90s, a new and innovative brake disk technology entered the high performance passenger car market. Approx. 2 years later, small volume production of carbon-ceramic brake disks started. In the past ten years the number of cars equipped with the new generation of ceramic matrix composite (CMC) brake disks has continuously increased, with main usage in low volume, high horse power applications. The goal of this paper is to give an overview of the system specific boundary conditions as well as today's and tomorrow's targets and aspects of friction material development used in CMC-disk based brake systems. Starting with a description of the system component properties, a comparison of typical CMC vs. standard gray cast iron disk (GCI) applications will be made. The impact of the component properties, especially the disk as friction counterpart to the pad, will be shown by comparing industry standard test scenarios.
2014-04-01
Technical Paper
2014-01-1009
Yoon Cheol Kim, Seong Jin Kim, Jaeyoung Lee, Jeongkyu Kim, SooHyuk Lee, Kyoungdon Yi, KiJeong Kim
Abstract Reducing unsprung mass of the car is a representative method to enhance the ride & handling performance and fuel efficiency. In this study, brake disc weight is reduced 15∼20% using a hybrid type material. The basis for this study is the separation of the friction surface and HAT(mounting part). Aluminum material is applied in the HAT for a light weight effect. Gray iron is applied in the friction surface section to maintain braking performance. Two types of joining between aluminum and cast iron are developed. One is the aluminum casting method utilizing a gray iron insert and the other is a bolted assembly method. Detailed structure, process and material are optimized using try-out & dynamometer experiments. The Reliability of this development is proved through durability (dynamometer and vehicle) testing.
2014-04-01
Journal Article
2014-01-0869
Guangqiang Wu, Shuyi Jin
During a car launch, the driving torque from driveline acts on brake disk, and may lead the pad to slip against the disk. Especially with slow brake pedal release, there is still brake torque applies on the disk, which will retard the rotation of disk, and under certain conditions, the disk and pad may stick again, so the reciprocated stick and slip can induce the noise and vibration, which can be transmitted to a passenger by both tactile and aural paths, this phenomenon is defined as brake groan. In this paper, we propose a nonlinear dynamics model of brake for bidirectional, and with 7 Degrees of Freedom (DOFs), and phase locus and Lyapunov Second Method are utilized to study the mechanism of groan. Time-frequency analysis method then is adopted to analyze the simulation results, meanwhile a test car is operated under corresponding conditions, and the test signals are sampled and then processed to acquire the features.
2013-09-30
Technical Paper
2013-01-2056
Toshikazu Okamura
The surface texture of a brake disc in some cases affects the braking effectiveness of a vehicle in the early stages of use. Brake discs usually turn in one rotational direction during their finishing process but are turn in two directions on a vehicle. This causes a difference in friction or wear between two wheels. Directional surface textures of brake discs finished by turning or roller burnishing may cause this interaction to become more severe than those finished by grinding. Full-scale tests using actual friction pairs are effective for estimating the total braking performance of a full vehicle or its corners. However, they are exposed to various factors and different brake-disc locations creating different friction and wear histories. The author, therefore, concluded that fundamental experiments using small-scale specimens are necessary to examine the details of the interaction between the disc surface texture, rotational direction, and friction material.
2013-09-30
Journal Article
2013-01-2039
David B. Antanaitis
Driving on the race track is an especially grueling situation for the automotive brake system. Temperatures can exceed the phase transition temperature of the disc material, wear rates of friction material can be orders of magnitude higher than during street use, and hydraulic pressures and mechanical stresses on components can approach their design limits. It is a given that friction material under these conditions will wear unevenly - causing taper and cupping wear - and an associated set of performance degradations will occur, including an increase in fluid consumption (pedal travel increase) and loss of mechanical efficiency (pedal force increase).
2013-09-30
Journal Article
2013-01-2053
SeongJoo Lee, ShinWook Kim, ShinWan Kim, SeongKwan Rhee
Two sets of OE quality brake discs were evaluated for their equivalence in friction and wear under a humidity controlled condition in order to avoid the influence of humidity on friction and wear. These discs were received from two different suppliers located in two different countries. Small differences were found in disc chemistry and microstructure, which resulted in differences in disc properties, and friction and wear characteristics. It is recommended that extreme care must be exercised in determining the performance equivalence of one disc from one supplier against another disc from a second supplier.
2013-07-15
Journal Article
2013-01-9116
Ali Belhocine, Mostefa Bouchetara
The main purpose of this study is to analyze the thermomechanical behavior of the dry contact between the brake disc and pads during the braking phase. The simulation strategy is based on computer code ANSYS11. The modeling of transient temperature in the disc is actually used to identify the factor of geometric design of the disc to install the ventilation system in vehicles. The thermal-structural analysis is then used with coupling to determine the deformation and the Von Mises stress established in the disk, the contact pressure distribution in pads. The results are satisfactory when compared to those of the specialized literature.
2012-09-17
Technical Paper
2012-01-1809
Anish Poudel, Tsuchin Chu, Peter Filip
This paper discusses the application of an air-coupled ultrasonic non-destructive evaluation (NDE) method for aircraft braking materials. The main objective of this research work was to identify and characterize flaws such as delaminations, cracks, porosity (resin pockets), and disbonds in commercial Carbon/Carbon (C/C) composite aircraft brake disks. Air-coupled ultrasonic testing (ACUT) method was applied for the inspection of commercial C/C brake disks. Several tests were performed by using various air-coupled ultrasonic transducers at center frequencies 50, 120, 125, 225, 400, and 436 kHz in a through-transmission mode by varying scan increments and resolutions. It was found that a testing frequency of 125 kHz provided the best results for commercial C/C composite aircraft brake disks. The relative through-transmitted ultrasonic signal drop in the defect areas was around −18 dB which allowed for easy distinction of abnormal regions within the C/C brake disks.
2012-09-17
Technical Paper
2012-01-1807
Young Min Kim, Ju Young Kim, Jeongkyu Kim
In order to reduce brake squeal noise, it is important to identify operational deflection shape (ODS) of brake disc while squeal arises. However, in the conventional modal analysis and optical measurement, it is only able to identify limited ODS because of the technical limits. This paper details the test method to identify ODS in radial and tangential as well as axial direction of a brake disc in driving condition. Vibrational signal of a rotating disc was obtained by triaxial accelerometer installed to solid type discs/cooling fins of ventilated type discs, then ODS of disc were analyzed through digital signal processing.
2012-09-17
Technical Paper
2012-01-1804
Gabriel Hurel, Jean-Frédéric Diebold lng, Sébastien Besset, Louis Jézéquel
Aeronautical brakes are subject to non-linear unstable vibrations. In particular, two modes appear and present a risk for the structure. Firstly, the whirl modes consist of a rotating bending motion of the axle out-of-phase with the brake torque tube. It is due to a coupling of two bending modes of the axle in orthogonal directions. Secondly, the brake squeal mode resulting from stick-slip or sprag-slip phenomena consists of a rotational motion of the brake around the axle. Those vibrations are not resulting from an external excitation but are friction-induced self-excited. Hence, they are dependent on tribological phenomena specific to carbon disks and are in particular controlled by the friction coefficient μ. In order to take into account the dynamical aspect in brake design, Messier-Bugatti-Dowty wants to simulate modes and acceleration g's levels. This article deals with the improvement of such a model. A finite element of the brake exists.
2012-09-17
Technical Paper
2012-01-1836
Fabrizio Merlo, Umberto Passarelli, Diego Pellerej, Pietro Buonfico
Brake pad material formulation and disc microstructure/composition plays a mutual role during wear test due to the third body layer (TBL) formation and its relative evolution due to temperature change. Nevertheless these ones could influence corrosion behavior. In this study we investigated the effect of rotors characteristics on wear and sticking behavior. Rotor and brake pad microstructure were analysed with optical, metallographic and scanning electron microscope to understand the surface and TBL evolution (using different thermal preconditioning) taking into consideration also the copper role during the different wear stages. During this preliminary study we were able to find out different copper smear morphologies depending on test conditions and rotors features.
2012-09-17
Technical Paper
2012-01-1833
Arthur L. Swarbrick, Houzheng Wu
Previous research has highlighted that the formation of a sustained friction film, desired for stable and predictable friction performance, is highly dependent upon the region of the substrate (CMC) being examined. In attempt to improve the friction performance, notably bedding-in, research at LU has been developing coatings aimed at ensuring friction film development across the substrate. This paper focuses on the performance of one of these coating formulations, and examines the performance of this on a laboratory scale dynamometer. Subsequently, the coating has then been applied to a full size brake disc, as used on a prestige vehicle, for dynamometer testing at an industry scale for comparative purposes. On both lab and full scale samples the bedding performance shows improvements over the standard material, and at the full scale the coating indicates improved stability of subsequent friction performance through a modified AK Master test schedule.
2012-09-17
Journal Article
2012-01-1822
Toshikazu Okamura, Hiroyuki Yumoto, Masanori Imasaki
The propensity of brake squeal depends significantly on the vibrational characteristics of disc rotors. In this study, we focused on the differential effects of disc dimensions on the natural frequencies of various vibration modes. We analyzed the results of the CAE factorial experiments presented in our previous paper, which were conducted on four disc rotors with different designs such as front-and back-vented and solid discs. As a result, the effects of disc dimensions on natural frequencies were confirmed to depend on vibration modes, their orders (or the number of nodal diameters), and the basic design of disc rotors. The dimensions that change the stiffness of the friction ring such as ventilation-path width and fin thickness had larger effects on the out-of-plane circumferential modes of high orders than those of low orders. The dimensions around the necking, on the other hand, had a large effect on the low-order modes.
Viewing 1 to 30 of 74

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